channel layer Flush extension: rename close to aclose?

[devkral]

I am not quite sure but it seems as there is a python convention to name an async close function "aclose".
For example this name is used in contextlib.aclosing.
A rename would ease to write tests or adapters for layers as we can simply reuse contextlib.aclosing.

Note: this is not a big issue. What aclosing does is easy to replicate with the close method (see python documentation).

[devkral]

^What aclosing does is easy to replicate with a different named close method.

Modified example

from contextlib import asynccontextmanager

@asynccontextmanager
async def aclosing_modified(thing):
    try:
        yield thing
    finally:
        await thing.close()

[carltongibson]

@devkral I haven't had a chance to really think about this yet, but it's on my list.